We have established a Consortium Tissue Core to process, store, and distribute samples from patients with[unreadable] Chronic Lymphocytic Leukemia. One of the aims of this proposal is to continue to serve as a repository for[unreadable] all CLL samples from patients diagnosed and collected at the participating CRC clinical sites. The[unreadable] processing, storage, and distribution of each sample will be performed according to established standard[unreadable] operating procedures in accordance with HIPAA regulations. The Tissue Core will also perform a basic set[unreadable] of assays on all viably stored CLL samples from each patient upon initial receipt. These tests will include:[unreadable] immunophenotyping to determine the surface antigen phenotype, ZAP-70 expression, and determination of[unreadable] the expressed immunoglobulin heavy chain gene (IgVH) mutational status. Testing for Minimal Residual[unreadable] Disease (MRD), soluble CD20/CD52 (rituximab/alemtuzumab), and B CLL turnover rates will be performed[unreadable] on specific CLL samples enrolled in clinical trials during follow-up and pre & post therapy as needed. In[unreadable] addition, the serial samples of specific CLL patients will be characterized according to their surface antigen[unreadable] phenotype by multiparameter flow cytometric analysis. This will allow the CRC investigators to examine for[unreadable] longitudinal changes in the leukemia cell's genotype, biochemistry, and/or immunologic phenotype and[unreadable] correlate these data to clinical outcome. The Tissue Core will seek to standardize interphase Fluorescence[unreadable] in situ Hybridization (FISH) studies by distributing specific characterized CLL samples to the participating[unreadable] CRC cytogenetics sites at which FISH analysis will be conducted. This validation will provide innovative and[unreadable] accurate interphase FISH studies for CRC clinical trials and research investigators. The Tissue Core will[unreadable] also collect, process, and validate specimens from affected family members with CLL for targeted genetic[unreadable] studies performed by CRC investigators. Finally, the Tissue Core will distribute specific characterized[unreadable] samples as requested by CRC investigators for hypothesis driven studies. This trafficking of characterized[unreadable] CLL samples, with their associated clinical and demographic data, will enable and facilitate the development[unreadable] of new CLL therapies.